In order to study the film pressure characteristics of mechanical seals of high-speed and low-temperature turbopump under two-phase condition,based on the theory of homogeneous flow,the axisymmetric phase change model of mechanical seals fluid film including thermal effect,centrifugal inertia effect and actual gas effect was established.The influence mechanism of centrifugal inertia term on the pressure and phase change of fluid film was analyzed with liquid oxygen as sealing medium.The results show that the external pressure mechanical seal film pressure decreases and the phase change level increases when considering the centrifugal inertia term.Under isothermal conditions,the film pressure coefficient has an unstable peak with the increase of medium temperature.In non-isothermal conditions,the slight change of medium temperature will affect the stability of seal operation.When the medium temperature is more than 90 K,the increase of medium pressure decreases the film pressure coefficient,but enhances the sealing stability.When the film thickness is 2.0 μm,there is a maximum film pressure coefficient,and the sealing bearing capacity is larger but the sealing stability is poor.